This invention relates to timepieces, and more particularly to wrist watches having conventional hour-indicating and minute-indicating radial arms or hands, and additionally, a second-indicating means disposed above the hour and minute-indicating hands. Conventionally, the second-indicating means is also a hand which generally is at least as long as and lighter in weight than the minute hand, which in turn is longer and lighter in weight than the hour hand. The second hand is long and slender because it is essential that the second hand have relatively low mass to maintain the precision to which the delicate mechanism of a conventional watch is dedicated.
Recently it has become desirable to use rotatable disc members instead of the conventional hands of clocks and watches. This use of rotatable disc members is in part due to the dictates of fashion but is also due, in large measure, to the greater visual impact of the rotating reference characters or indiciae on the disc members. Particularly in poor light conditions the reference character on a rotatable disc is much easier to see than a slender second hand. Thus, a timepiece having three rotatable transparent discs mounted coaxially within a case, beneath a graticule marked on the surface of the cover glass, is described in U.S. Pat. No. 3,665,702. Still another timepiece utilizing colorgraduated discs is disclosed in U.S. Pat. No. 3,803,831, and it is stated therein that disc members are preferable to watch hands because watch hands are more often than not quite fragile, particularly the second hand. This particular fragility of the second hand, and its proclivity to be deleteriously affected by even the minimal presence of foreign material in the form of fine particles of dust is also alluded to in U.S. Pat. No. 2,976,674 which describes an open-face clock. In this clock the second hand is sealed in an enclosure designed to isolate the annular space between the surface of the spindle on which the second hand is mounted and the inner surface of the tubular member in which the spindle turns.
The same problem of maintaining a clean annular space between the central spindle for the second hand and a surrounding spindle for the minute hand exists in a conventional wrist watch, except of course to a lesser degree because of the protective cover member or cover glass on a wrist watch. However, as is well known in the art, moisture and microscopic dust particles nevertheless do find their way into a watch casing. This disconcerting inability to completely seal a watch casing with a cover glass is commonly attributed to the observation that a watch "breathes" as part of the physical process by which it establishes and adjusts its equilibrium with the conditions of the surrounding atmosphere.
Thus the combination of the relatively large mass of a rotatable disc member substantially the same diameter as that of the face of the watch and the deleterious effect of dust in the annular space between the central spindle on which the second-indicating means is to be mounted, has made it most difficult to provide a reliable rotating second-indicating disc member for a wrist watch. As is well known a watch removably disposed on a person's wrist is subject to many disruptive movements and it is particularly difficult to provide a mounting means for a second-indicating disc member which mounting means can effectively negate such disruptive movements. The second-indicating disc member of this invention mounted in the unique manner to be described more fully hereinafter, provides a solution to the problem.